This is total nonsense. If plants were converting oxygen from water at such a rate, the seas would be dropping constantly and would have almost dissappeared by now. Truth of the matter is that the earth is a very well balanced eco-system and has been so for as far back as we can tell.
Huh, I don't follow at all.
Do you ever run the numbers before making such statements? Don't you know anything about science? You're the one claiming to have a leg up on everything, so work out the amount of water required to make an atmosphere of 21 percent oxygen. We'll make it somewhat easier for you:
• Figure the Earth's atmosphere to be about 150 kilometers deep (this is close enough for government work).
• Assume, also that the hydrogen part eventually bleeds off into space (which is what really happens).
• The diameter of the Earth is 12,756 km.
• According to this site, oxygen makes of 88.81 percent of pure water by weight.
• According to this site, air weighs 1.2 kilograms per cubic meter.
• This site says that oxygen makes up 23.15 percent of the atmosphere by weight, or 0.2778 kilograms per cubic meter of air, and 85.8 percent of seawater by weight (858 kilograms per cubic meter).
The last point means that for every cubic meter of sea water you get a little more than three cubic meters of atmospheric oxygen.
I'll let you work out just how many cubic meters of seawater had to be converted to get the current atmosphere. With actual numbers, you can make an argument, rather than just throwing out stuff willy-nilly Mr. 21st century scientist.
Water is consumed by photosynthesis, yes. (You make it sound as if plants were electrolyzing water to release their oxygen. Sheesh!) It is released when the sugars resulting from the photosynthesis are metabolized by the plant (or whatever eats the plant). The net loss of water from photosynthesis is probably not important, no bigger than the total amount of sugar in the world at a given time. We have a lot more water than sugar.
Truth of the matter is that the earth is a very well balanced eco-system and has been so for as far back as we can tell.
We have direct evidence that the balance has swung many times. All kinds of things have changed drastically: temperatures, ice cover, the oxygen content of the atmosphere, sea levels, the nature of the animals and plants . . .
Because I don't trust you will ever actually run the numbers to back up your assertion, I've decided to give it a go, myself.
First off, we need to determine the volume of the atmosphere. The simplest way to do this is to determine the volume of the Earth and atmosphere together and then subtract the volume of the Earth.
The Volume of a Sphere is:
4 * Pi * (radius)^3
-------------------
3
We'll round Pi to 3.1416 for ease of calculation.
As mentioned earlier, the diameter of the Earth is 12,756 kilometers. Half of this is 6,378. To this we'll add the 150 kilometers of the atmosphere for 6528 kilometers. The volume of the who kit and kaboodle comes to 1,165,279,381,527 cubic kilometers (~1.17 trillion cubic kilometers).
Now, we'll work out the volume of the Earth, itself. Using a radius of 6,378 kilometers we come up with 1,086,783,833,910 cubic kilometers.
This means the atmosphere is 78,495,547,617 cubic kilometers.
Now, earlier we said one cubic meter of sea water supplies the oxygen for 3088.6 cubic meters of atmosphere. There are 1 million cubic meters in a cubic kilometer, so one cubic meter of sea water supplies the oxygen for 0.0030886 cubic kilometers of atmosphere. Therefore, it takes only 25,414,605 cubic kilometers of seawater to generate the atmosphere we have around Earth.
"Wait!" you say. "25 and a half million cubic kilometers of seawater is a lot of seawater." Let's see just how much that really is.
According to this Woods Hole site, the average depth of the ocean is 3.5 to 4 kilometers. We'll split the difference and say 3.75 kilometers. BTW, the above site is for grade schoolers, so it should be fairly simple to follow.
The surface area of a sphere is Surface Area of a Sphere = 4*Pi*r^2. Using this formula, we determine the surface area of the Earth to be 511,187,128 square kilometers. Water covers about 70 percent of this area, or 357,830,990 square kilometers. At an average depth of 3.75 kilometers, this gives us 1,341,866,211 cubic kilometers of water. It turns out you'd need to covert only about 2 percent of the Earth's water to hydrogen and oxygen to get the atmosphere we have. In 4.5 billion years, this has only lowered the oceans by 75 meters -- not a pittance, but certainly not anywhere near drying them up.
You know, these calculations can also be used to determine the amount of water required by Noah's flood:
"Fifteen cubits upward did the waters prevail; and the mountains were covered." Gen 7:20
A cubit was about 1½ feet, so the mountains were covered to a depth of 22.5 feet. The highest mountain in the world is Mt. Everest, of course, at a height of 29,001 feet. This means that the world had to be covered to a depth of 29,024 feet, or about 9 kilometers. We know the surface area of the Earth is 511,187,127, so we'd need an additional 4,600,684,143 cubic kilometers of seawater, or 3.5 times the total amount of water on Earth now.
See how absurd some claims are when one starts to run the numbers?
This is total nonsense. If plants were converting oxygen from water at such a rate, the seas would be dropping constantly and would have almost dissappeared by now. Truth of the matter is that the earth is a very well balanced eco-system and has been so for as far back as we can tell.
-- gore300
This is such a staggeringly ridiculous strawman model of anything going on in the real world, I just wanted to blow it up a little bigger as a monument to Cretin Science.
When you do photosynthesis, sunlight in the presence of the catalyst chlorophyll energizes water and carbon dioxide to form glucose and free oxygen. (More complex carbos can form in other reactions with the glucose later but this is the step that consumes a little water.)
When you burn/metabolize the glucose (or any carbohydrate) with free oxygen you get the water and carbon dioxide back. You also get some of the solar energy that was stored chemically in the glucose.
The only water not returned to the system is the water and carbohydrate content of the biomass itself. Period. The only way for the ocean to dry up from bioactivity was for the ocean to turn completely into sugar, starch, cellulose, etc. There probably are a lot of limiting factors that put you in equilibrium before that happens. (Not enough carbon or other essential elements, etc.)